Thermoplastic olefin alloys and method for producing the same

ABSTRACT

A thermoplastic olefin comprising an alloy of an olefin copolymer elastomer and a propylene/comonomer random copolymer is provided. The comonomer is selected from one or more of ethylene and C 4  to C 10  alpha-olefins. Polypropylene is an optional component of the alloy. The alloy may be produced by melt blending, reactor blending or a combination thereof, of the various components.

This application is a continuation-in-part of U.S. Ser. No. 140,462,filed 1/4/88, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates generally to thermoplastic elastomercompositions. More particularly, the present invention relates tothermoplastic olefin alloys of olefin copolymer resins and olefincopolymer elastomers.

Rubber products have generally found extensive use in applications whichrequire elasticity and flexibility. Molding of rubber into a finishedproduct entails a curing step, generally referred to as vulcanization,which requires the use of specialized molding machines, long cycle timesand a number of complicated processing steps. The rubber moldingprocess, therefore, does not lend itself to mass production due to theseprocessing difficulties. It would be highly desirable to find a rubbersubstitute which has the desirable properties of rubber without the needfor a vulcanization step.

Many attempts have been made to find such rubber substitutes. Forexample, flexible plastics such as flexible vinyl chloride resins,ethylene/vinyl acetate copolymers and low density polyethylenesgenerally have good flexibility, fabrication and molding properties, butsuffer from poor heat resistance, impact strength and resiliency(rebound) which greatly restrict their utility.

In order to improve the properties of such flexible plastics, they havebeen blended with high melting point plastics such as high densitypolyethylene and polypropylene. This blending, however, causes a loss inflexibility. Also molded articles of good quality cannot be produced dueto flowmarks, sinkmarks and other imperfections which may occur duringthe molding process.

More recently, a class of compounds having properties between those ofcured rubbers and soft plastics are being investigated. These compoundsare generally referred to as thermoplastic elastomers (TPE). Theclassical TPE structure involves a matrix of an elastomer such as, forexample, a polybutadiene, polyester or polyurethane, with a crosslinkednetwork tied together by thermoplastic junction regions. A well knownexample of a TPE is Shell's Kraton® G, an SBS triblock of styrene andhydrogenated polybutadiene, where the thermoplastic crosslinking pointsare small domains of glassy polystyrene held together by polybutadieneblocks. This structure leads to behavior similar to vulcanizedelastomers but, at temperatures above the polystyrene softening point,the system undergoes plastic flow.

A subset of thermoplastic elastomers, embodying only olefin basedpolymers, is referred to as thermoplastic olefins (TPO). A typical TPOcomprises a melt blend or like mixture of a polyolefin resin, generallypolypropylene, with an olefin copolymer elastomer (OCE). The polyolefinresin will give the TPO rigidity and temperature resistance while theelastomer imparts flexibility and resilience as well as improving thetoughness of the material.

TPOs find particular application in the auto industry for flexibleexterior body parts such as, for example, bumper covers, nerf strips,air dams and the like. In such applications, it is desired that the TPOhave good resiliency (ability of the part to return to its originalshape after deformation), impact strength at low temperatures,flexibility, high heat distortion temperature, surface hardness andsurface finish characteristics. Additionally ease of processability andmolding is desired.

Other applications for TPOs include films, footwear, sporting goods,electric parts, gaskets, water hoses and belts, to name just a few.Particularly in films, elasticity and clarity properties are important.Other of the aforementioned properties will be important depending uponthe desired application.

The prior art discloses a wide variety of TPOs and processes forproducing the same. For example, U.S. Pat. Nos. 3,806,558 and 4,143,099(both incorporated by reference herein for all purposes as if fully setforth) teach a TPO comprising a blend of an olefin copolymer elastomer,typically an ethylene-propylene or ethylene-propylene-nonconjugateddiene elastomer, with a polyolefin resin, typically polypropylene. Theblend is produced by mixing these two components in the presence of anorganic peroxide curing agent to partially cure the elastomer.

In order to yield such a TPO with good flexibility and heat distortionresistance, however, it has been necessary to use 50% or more by weightof the OCE. This high OCE content produces a TPO which is not verysuitable for injection molding due to poor melt flow propertiesresulting in flow lines, weld lines and other surface imperfections inthe molded parts. Additionally, the OCE is a more expensive component ofthe TPO, and the use of less OCE is highly desirable to lower productcosts.

SUMMARY OF THE INVENTION

The present invention, therefore, provides a TPO having desirableresiliency, impact strength, flexibility, heat distortion, surfacehardness, surface finish, elasticity, clarity and moldability propertiesdepending upon the desired end use.

The present invention also provides such a TPO which utilizes less OCEthan conventional TPOs.

Additionally, the present invention provides methods for producing suchTPOs whereby the aforementioned properties may be easily tailored tosuit the desired end use without the use of a costly blending orcompounding step.

In accordance with the present invention, there is provided a TPO which,in its overall concept, comprises an alloy of (1) from about 12% toabout 23% by weight, based upon the weight of the alloy, of an olefincopolymer elastomer (OCE); (2) from about 25% to about 88% by weight,based upon the weight of the alloy, of a random copolymer (RCP) resin ofpropylene and ethylene; and (3) from 0% to about 33% by weight, basedupon the weight of the alloy, of polypropylene.

These three principal components may be blended, formed or otherwisemixed by any one of a number of suitable methods to produce the TPOalloys of the present invention. For example, the TPO may be produced bymelt blending the various components or by reactor blending the RCPand/or OCE then melt blending with the other components as furtherdetailed below.

TPOs in accordance with the present invention offer numerous advantagesover conventional formulations. For the same degree of flexibility, thepresent TPOs can be formulated to contain much less OCE thanconventional TPOs. This yields a product with molding performancesimilar to that of polypropylene, and significantly higher heatresistance and lower cost than prior TPOs due to the use of less OCE.

Because of the additional variables of utilizing three components (theRCP, OCE and polypropylene) in the alloy, with the capacity to alter thecomonomer content of the RCP, the properties of the alloy can betailored in a much more precise fashion. The methods for producing thesealloys, as detailed below, easily allow for this tailoring.

These and other features and advantages of the present invention will bemore readily understood by those skilled in the art from a reading ofthe following detailed description with reference to the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustrating several preferred process schemes forproducing TPO alloys in accordance with the present invention.

FIG. 2 is a schematic illustrating a preferred sequential reactor schemewhich may be utilized in producing TPO alloys in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As previously indicated, the thermoplastic olefins (TPO) of the presentinvention, in their overall concept, comprise an alloy of an olefincopolymer elastomer (OCE) with a random propylene/monoolefin copolymer(RCP) resin. Polypropylene may also be included as a component of thealloy. Alloy, as that term is used herein, means any various blend orother like mixture of the various components.

The OCE is utilized in the alloy in amounts ranging from about 12% toabout 23% more preferably from about 15% to about 20% by weight basedupon the weight of the alloy. The OCE is added to impart flexibility,resilience and toughness, particularly at lower temperatures, to thealloy. The inclusion of lower amounts of the OCE, however, willgenerally improve surface hardness, heat distortion, appearance andprocessability properties of the TPO alloys while also generallylowering their cost of manufacture.

The OCE comprises an elastomeric random copolymer of two or moremonoolefins. Normally one of the monoolefins is ethylene and another isa C₃ to C₁₀ alpha-olefin such as, for example, propylene, 1-butene and1-hexene. Suitable OCEs include, for example, an ethylene-propylenecopolymer elastomer or an ethylene-propylene-nonconjugated dieneterpolymer elastomer. The nonconjugated diene, for example, may bedicyclopentadiene, 1,4-hexadiene, dicyclooctadiene, methylenenorborneneor ethylidenenorbornene.

The OCEs useful in the alloys of the present invention preferably have aMooney viscosity greater than about 20 (ML(1+8) at 212° F.), morepreferably, between about 20 to about 120, most preferably between about35 to about 85. The percentage of ethylene in the OCE should be greaterthan about 30% by weight, more preferably between about 40% to about 80%by weight, but the particular amount has not been found to be criticalto the invention. When a terpolymer OCE is utilized, the OCE generallycomprises from about 1% to about 10% by weight of the nonconjugateddiene, but again the particular amount has not been found critical tothe invention.

OCEs having the above-described properties and methods for making thesame are well known in the art, and are readily available commerciallyfrom a number of manufacturers. These elastomers may also be produced ina sequential reactor as described below.

The propylene/monoolefin RCP is utilized in the alloy in amounts rangingfrom about 25% to about 88% more preferably from about 50% to about 88%by weight based upon the weight of the alloy. The propylene/monoolefinRCP is added to control the flexibility of the alloy as well as toimpart a better balance between the flexibility, heat resistance andmoldability characteristics of the alloy. The RCP may also improve theheat distortion, low temperature impact and surface hardness propertiesof the TPO alloy. Since the RCP allows control of the flexibility, theuse of the OCE can be restricted to only the amount required to impartthe desired resilience and toughness properties.

As just indicated, the RCPs useful in the alloys of the presentinvention comprise a random propylene/ethylene copolymer.

The RCP comprises an ethylene content from about 3% to about 8%, morepreferably from about 4% to about 6%, by weight based upon the weight ofthe RCP.

Such RCPs may have a wide range of melt flow rates (MFR), generally upto about 100 g/10 minutes (ASTM D1238, Condition L), as well as wideranging molecular weight distributions (MWD). As used herein, MWD can beestimated from the ratio of the MFR at 230° C., 10000 g, to the MFR at230° C., 2160 g (melt flow ratio).

Such RCPs may be produced by polymerizing propylene and ethylene in thepresence of any one of a number of well-known Ziegler-type catalystssuitable for producing propylene-based random copolymers. Particularlypreferred catalysts and processes are those described in U.S. Pat. Nos.4,127,504, 4,330,649 and 4,543,400, all of which are incorporated byreference for all purposes as if fully set forth.

Polypropylene is utilized in the alloy in amounts ranging from 0% toabout 33% by weight based upon the weight of the alloy. Polypropylene isgenerally added to the TPO alloy to improve its thermoplasticity,stiffness, heat distortion, surface hardness and processabilityproperties.

Polypropylene useful in the alloys of the present invention is normallysolid and isotactic, i.e., greater than 90% hot heptane insolubles,having an MFR of from about 0.1 to about 100 g/10 minutes. As is known,such polypropylene is normally crystalline with a density range fromabout 0.89 to about 0.91 g/cc. Preferably, a polypropylene having an MFRbetween about 0.2 to about 12.0 is employed. Also it is preferred thatthe polypropylene have a melt flow ratio of from about 10 to about 50.The polypropylene may also include minor amounts of ethylene and/orother monoolefins such as, for example, 1-butene or 1-hexene, in amountsup to about 3 mo1 %. The actual properties of the polypropyleneemployed, of course, will be chosen based upon the method of producingthe alloy and ultimate use of such alloy.

Such polypropylenes and methods for making the same are well-known inthe art and are readily available commercially from a number ofmanufacturers.

Pigments, fillers, stabilizers, antioxidants, ultra-violet screeningagents, antistatic agents, nucleating agents, certain processing oilsand the like may optionally be included within the present TPO alloys;however, this should not be considered a limitation of the presentinvention.

The three principal components, i.e., polypropylene, RCP resin and OCE,may be blended, formed or otherwise mixed by any one of a number ofsuitable methods to produce the TPO alloys of the present invention.

For example, the TPO alloy may be produced by melt blending in one ormore stages the desired amounts of RCP resin, polypropylene and OCE,within the ranges described above, under intense mixing conditions at atemperature of between about 175° C. to about 250° C. for a timesufficient to insure that the components are adequately integrated.Additionally, more than one type or form of each of the components maybe concurrently utilized. This melt mixing can be accomplished in, forexample, a Banbury mixer, Farrel Continuous mixer, single screwextruder, twin screw extruder or the like. The resulting alloy may bepelletized or otherwise processed for storage or further use.

To adjust the melt flow properties of the resulting alloy, one or moreorganic peroxides may be added during this melt mixing. The organicperoxide will react with the RCP resin and polypropylene to cause somemolecular decomposition, resulting in an overall decrease in molecularweight and, consequently, increase in the MFR. If a non-conjugated dieneOCE terpolymer is utilized, some slight degree of crosslinking may occurbetween the OCE molecules, but this small amount of crosslinking has notbeen found to substantially affect the properties of the TPO alloy soproduced. Otherwise, the organic peroxide does not substantially affectthe OCE.

These decomposition processes and suitable organic peroxides are wellknown in the art. For example, U.S. Pat. Nos. 4,143,099 and 4,212,787disclose decomposition processes and numerous suitable organicperoxides, and are incorporated by reference herein as if fully setforth. Suitable organic peroxides include, for example, dicumylperoxide, di-tert-butyl peroxide and2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

The organic peroxides are utilized in amounts ranging from about 100 toabout 2500 parts per million by weight based upon the weight of the RCPresin and polypropylene. The RCP resin and, optionally, polypropyleneand OCE, are melt mixed under the aforementioned temperature conditionsuntil the desired degree of molecular breakdown, i.e., the desired MFR,has occurred. It is well within the skill in the art to choose theparticular organic peroxide, mixing conditions, temperature and timebased upon the physical properties of the initial resins and desired endMFR.

Referring now to FIGS. 1 and 2, there is schematically illustrated anumber of other preferred processing schemes for producing TPO alloys inaccordance with the present invention. In all of the various processschemes, the RCP resin is produced in a reactor system generallydesignated as 10.

Referring now to FIG. 1, a propylene stream (PR), comonomer stream (COM)and catalyst (CAT) are fed into reactor system 10. As depicted in FIG.1, reactor system 10 comprises a first reactor 12 for producing thedesired RCP resin. It should be noted, however, that reactor system 10and first reactor 12 may comprise a single reactor or a sequentialseries of reactors as further detailed below.

As previously mentioned, the propylene and comonomer(s), preferablyethylene, are polymerized in the presence of any one of a number ofwell-known Ziegler-type catalysts suitable for producing randompropylene-based copolymers. An especially preferred catalyst systemcomprises a titanium trichloride catalyst component, diethyl aluminumchloride co-catalyst and methyl methacrylate modifier, such as disclosedin the aforementioned incorporated references.

The propylene and comonomer(s) are preferably polymerized in a liquidphase reaction in, for example, a continuous stirred reactor attemperatures ranging from about 35° C. to about 85° C., more preferablyfrom about 45° C. to about 85° C., and pressures given by the vaporpressure of the various components.

A wide variety of RCP resins having varying comonomer concentrations andMFRs can be produced from reactor 12. Higher MFR resins can be directlyproduced in reactor 12 by the addition of a chain transfer agent suchas, for example, hydrogen or diethyl zinc, during the polymerizationreaction. The higher MFR resins so produced will preferably have an MFRof between about 1 to about 35, more preferably between about 5 to about20, g/10 minutes. The addition of these chain transfer agents, however,will also limit the amount of comonomer which can be incorporated intothe RCP resin without excessive agglomeration of particles and resultingprocessing difficulties and, therefore, is not preferred.

Lower MFR resins may be produced by excluding the aforementioned chaintransfer agents from the polymerization reaction. This results in a veryhigh molecular weight and very low MFR RCP resin, and allows theincorporation of much higher amounts of comonomer into the RCP resinwithout the aforementioned processing problems. It is preferred,therefore, that the low MFR resin produced from reactor 12 have an MFRof less than about 1.0 g/10 min., more preferably, less than about 0.1g/10 min.

Referring back to FIG. 1, it can be seen that the RCP resins producedfrom reactor system 10 can be processed via several different paths toproduce alloys in accordance with the present invention. As one example(path A), the alloy may be blended by high shear melt mixing the RCPresin in a mixer 14 with the desired types and amounts polypropylene(PP), OCE and organic peroxide (PER), as described above.

As another example for processing the RCP resins from reactor system 10(path B), the RCP resins can be blended by melt mixing in a mixer 16with the desired types and amounts of organic peroxide (PER) and,optionally, polypropylene (PP). The resulting blend may then bepelletized or otherwise processed for transport or storage (thisintermediate step is generally designated as 18), and subsequentlyblended by high shear melt mixing in another mixer 20 with the desiredtypes and amounts of polypropylene (PP) and OCE to produce alloys inaccordance with the present invention.

As previously mentioned, reactor system 10 may comprise a sequentialseries of reactors. Referring now to FIG. 2, there is depictedschematically a preferred sequential reactor system in which, as before,a propylene stream (PR), comonomer stream (COM) and catalyst (CAT) arefed into first reactor 12. The resulting outlet stream 22 from firstreactor 12, which will generally comprise the RCP resin, unreactedpropylene, unreacted comonomer, residual chain transfer agent andcatalyst, is then directly fed into a second reactor 24. Additionalcomonomer (COM) and propylene (PR) are also fed into second reactor 24and a "reactor" blend of the RCP from first reactor 12 with a secondpropylene/monoolefin RCP is produced. The catalyst utilized in reactor12 acts as the catalyst for the reaction in second reactor 24.

"Reactor" blend, as that term is used herein, generally means a highlydispersed blend of two or more components produced as a result of theformation of one polymer in the presence of another. While some blockcopolymerization may take place during the reactor blending, the amountis so minimal as to not substantially affect the properties of the finalalloy.

The other reaction conditions in second reactor 24 are preferably thesame as those previously described for first reactor 12. A chaintransfer agent, as described above, may be utilized to control themolecular weight of the second RCP. It is preferred to ultimatelyproduce high molecular weight, low MFR (less than about 1.0 g/10 min.)RCP resin reactor blends from second reactor 24 and reactor system 10.

The RCP reactor blend from second reactor 24, therefore, may be tailoredto comprise varying comonomer contents and varying molecular weights byadjusting the feeds to reactors 12 and 24. For example, variation in theethylene content of the RCP allows for a product of relatively highsoftening point (good heat distortion resistance) for a given level offlexural modulus. Also, variation in the molecular weight of theproducts of the two reactors results in a broadening of the molecularweight distribution of the resulting RCP reactor blend. This broadeningallows products of superior heat sag (for thermoforming and blowmolding) and also products of low viscosity at high shear rates (forinjection molding).

The resulting RCP reactor blend from second reactor 24 can be processedvia paths A or B as described above or, in a most preferred variation,the outlet stream 26 from second reactor 24, which will generallycomprise the RCP reactor blend, unreacted propylene, unreactedcomonomer, residual chain transfer agent and catalyst, can be directlyfed into a third reactor 28 to which is also fed the ethylene (ET),comonomer (CON) and, if desired, nonconjugated diene (NCD) components ofthe OCE in the desired amounts. Preferably, the unreacted propylene andresidual chain transfer agent are removed from outlet stream 26 prior tofeeding into third reactor 28. The catalyst added to reactor 12 againacts as the catalyst for this reaction.

Unlike the reactions in reactors 12 and 24, the reaction in thirdreactor 28 is preferably a vapor phase reaction in, for example, amechanically agitated gas phase reactor at temperatures ranging fromabout 60° C. to about 80° C. and at pressures ranging from about 140psig to about 240 psig. The molar ratio of ethylene to total monomer inthe gas phase reactor will generally range from about 0.25 to about0.45.

The result from third reactor 28 is a second reactor blend of highlydispersed RCP resin and OCE. This second reactor blend may then directlybe utilized as the TPO alloy or may be further processed along paths Aor B as described above.

The alloys so produced by the aforedescribed methods will have wideranging physical properties suitable for a variety of applications. Forexample, compositions having very high melt strength can be producedover a range of stiffness values by utilizing broad molecular weightdistribution RCP reactor blends. These alloys will have particularutility for applications where the preferred fabrication technique isblow molding or vacuum forming. As another example, alloys which haverelatively low flexural modulus but which retain good heat distortionresistance may be produced by the use of ternary mixtures of variousRCPs, OCEs and polypropylenes. These alloys have particular utilitywhere a molded part is required to pass through a heating step.

The foregoing more general discussion of this invention will be furtherexemplified by the following specific examples offered by way ofillustration and not limitation of the above-described invention.

EXAMPLES

In the following examples, mechanical property evaluations were madeemploying the following tests:

(1) Melt Flow Rate--ASTM D-1238, Condition L.

(2) Flexural Modulus, secant--ASTM D-790.

(3) Shore D Hardness--ASTM D-2240.

(4) Notched Izod--ASTM D-256.

(5) Tensile Properties--ASTM D-638.

(6) Brittleness Temperature--ASTM D-746.

(7) Vicat Softening Temp.--ASTM D-1525.

(8) Shrinkage--ASTM D-995.

(9) Density--ASTM D-2240.

(10) Bending Beam Resiliency--a 5 in.×0.5 in.×0.125 in. specimen, heldby a 1/2 in. mandrel, is bent at an angle of 90° and held for 3 seconds.After release, the specimen is allowed 2 minutes of unstressed recovery.The angle from the normal is then measured and reported as resiliency.0° would constitute complete recovery and "perfect" resiliency.

The various materials utilized in the following examples are describedbelow, with the final alloy compositions, MFRs and densities presentedin Table I.

(A) PP-4092--a commercial crystalline polypropylene having an MFR ofabout 2 g/10 min., available from Exxon Chemical Company, Houston, Tx.

(B) Vistalon 719--a commercial ethylene/propylene copolymer elastomerhaving an ethylene content of about 77% by weight and a Mooney viscosityof about 78 (1+8, 100° C.), available from Exxon Chemical Company,Houston, Tx.

(C) RCP1--a propylene/ethylene random copolymer resin tailored to anethylene content of about 4.5% by weight with an MFR of about 0.3 g/10min. This RCP resin was produced by feeding 80 lb/hr propylene, 3 lb/hrethylene, 100 ppm by weight (based upon the propylene feed) of atitanium catalyst component, 650 ppm by weight (based upon the propylenefeed) of diethyl aluminum chloride and 15 ppm by weight (based upon thepropylene feed) of methyl methacrylate modifier into a first continuousstirred reactor operating at about 65° C. and a vapor pressure given bythe vapor pressure of the resulting liquid at this temperature. Theaverage residence time in the reactor was about 2.5 hours.

On a laboratory scale, the titanium trichloride catalyst component maybe prepared by adding 180 ml of 4M diethyl aluminum chloride (DEAC) over6 hours to 71.1 ml of neat TiCl₄ in 278.1 ml of hexane in a one literreactor at a temperature controlled between about -2° C. to about +2° C.Upon completion of the DEAC addition, the reaction was maintained forone hour, then heated at a rate of 120° C. to 20° C. then 2° C. to 65°C. and maintained at 65° C. for another hour. To the resultant brownishTiCl₃ solids with mother liquor was added 60 ml of hexane. This slurrywas contacted in a nitrogen purged one liter reactor equipped with anagitator with 55.8 g of propylene by passing propylene into the reactorat a rate of about 1 g/min. and at a temperature of about 38° C. toobtain a prepolymerized TiCl₃ comprising about 30 wt% polymer. Therecovered hexane washed (4× by decantation in 681 ml hexane at 60° C.and settling 1/2hour prior to decantation) prepolymerized TiCl₃ wet cakewas contacted in 116 ml hexane containing 109 g of hexachloroethane and90 g di-n-butyl ether. The reactor was heated to 85° C. and held at thistemperature for 5 hours with agitation. The recovered TiCl₃ catalyst waswashed 4× in hexane by decantation and dried to yield the finishedcatalyst component. For ease of feeding to the polymerization reactor,the catalyst component was used as a 30 wt % slurry in a mineral oil.

The catalyst actually used for these examples was prepared in ascaled-up version of this laboratory procedure.

The slurry from the first continuous stirred reactor was then fed to asecond continuous stirred reactor operating at about 65° C., to whichwas fed 35 lb/hr additional propylene, 0.2 lb/hr additional ethylene and500 ppm by weight (based upon the weight of the liquid propylene) ofhydrogen as a chain transfer agent. The residence time in this secondreactor was about 1 hour.

The slurry from this second continuous stirred reactor was washed bycontinuous countercurrent contacting with a mixture of propylene andn-butyl alcohol, then dried by heating at 100° C. in an agitated,nitrogen gas swept dryer.

(D) RCP2--a propylene/ethylene random copolymer resin tailored to anethylene content of about 6.0% by weight with an MFR of less than 0.1g/10 min. This RCP resin was produced as described above for RCP1 exceptthat the slurry from the first reactor was fed to the second reactoralong with 35 lb/hr additional propylene and 1 lb/hr additionalethylene. No chain transfer agent was added to the second reactor. Thesecond reactor was operated at about 60° C., and the average residencetime was about 1.5 hours.

                  TABLE I                                                         ______________________________________                                             WT %     WT %    WT %  WT %  MFR     DENS.                               EX.  PP-4092  V-719   RCP1  RCP2  (g/10 min.)                                                                           (g/cc)                              ______________________________________                                        C1   50       50      0     0     1.03    0.8927                              1    25       50      25    0     1.25    0.8900                              2    17       17      66    0     1.18    0.8920                              3     0       25      75    0     3.31    0.8895                              4    17       33      50    0     2.45    0.8907                              5    33       33      33    0     1.85    0.8930                              C2    0        0      100   0     6.46    0.8927                              6     0       50      50    0     1.76    0.8876                              7    17       17      0     66    2.76    0.8899                              8    25       50      0     25    1.16    0.8895                              C3    0        0      0     100   4.05    0.8876                              9    17       33      0     50    1.92    0.8890                              10    0       25      0     75    2.63    0.8875                              11   33       33      0     33    1.65    0.8900                              12    0       50      0     50    1.28    0.8850                              ______________________________________                                    

COMPARATIVE EXAMPLE 1

75 lbs. of PP-4092 and 75 lbs. of Vistalon 719 were tumble blended,extruded on a W.P. extruder then reextruded on a 60 mm Reifenhouserextruder to produce Sample 1. Sample 1 was injection molded in a 300 tonVan Dorn Model 300RS-14F-UHS injection molding press into standard partsfor the various ASTM tests, then tested for selected mechanicalproperties. The results are presented in Table II.

EXAMPLE 1

150 lbs. of RCP1 was admixed with Lupersol 101, a2,5-dimethyl-2,5-di(t-butylperoxy)hexane available from the LucidolDivision of the Penwalt Corp., Buffalo, N.Y., and extruded on a 60 mmReifenhouser extruder at 450° F. to an MFR of 5.5 g/10 min. to produceSample 2. 75 lbs. of Sample 2 was admixed with 75 lbs. of Vistalon 719in a barrel tumbler then extruder mixed on a W.P. extruder to produceSample 3. 6 lbs. of Sample 1 and 6 lbs. of Sample 3 were then tumblemixed, extruded on a 60 mm Reifenhouser extruder at 450° F., injectionmolded and tested as in Comparative Example 1. The results are presentin Table II.

EXAMPLE 2

4 lbs. of Sample 1 and 8 lbs. of Sample 2 were tumble mixed, extruded,molded and tested as in Example 1. The results are presented in TableII.

EXAMPLE 3

6 lbs. of Sample 3 and 6 lbs. of Sample 2 were tumble mixed, extruded,molded and tested as in Example 1. The results are presented in TableII.

EXAMPLE 4

4 lbs. of Sample 2, 4 lbs. of Sample 1 and 4 lbs. of Sample 3 weretumble mixed, extruded, molded and tested as in Example 1. The resultsare presented in Table II.

EXAMPLE 5

4 lbs. of Sample 2 and 8 lbs. of Sample 1 were tumble mixed, extruded,molded and tested as in Example 1. The results are presented in TableII.

COMPARATIVE EXAMPLE 2

12 lbs. of Sample 2 was extruded, molded and tested as in Example 1. Theresults are presented in Table II.

EXAMPLE 6

12 lbs. of Sample 3 was extruded, molded and tested as in Example 1. Theresults are presented in Table II.

EXAMPLE 7

150 lbs. of RCP2 was admixed with Lupersol 101 and extruded on a 60 mmReifenhouser extruder to an MFR of 1.0 g/10 min. to produce Sample 4. 8lbs. of Sample 4 and 4 lbs. of Sample 1 were tumble mixed, extruded,molded and tested as in Example 1. The results are presented in TableII.

EXAMPLE 8

75 lbs. of Sample 4 was tumble mixed with 75 lbs. of Vistalon 719 thenextruded on a W.P. extruder to produce Sample 5. 6 lbs. of Sample 5 and6 lbs. of Sample 1 were tumble mixed, extruded, molded and tested as inExample 1. The results are presented in Table II.

COMPARATIVE EXAMPLE 3

12 lbs. of Sample 4 was extruded, molded and melt blended as inExample 1. The results are presented in Table II.

EXAMPLE 9

4 lbs. of Sample 1, 4 lbs. of Sample 4 and 4 lbs. of Sample 5 weretumble blended, extruded, molded and tested as in Example 1. The resultsare presented in Table II.

EXAMPLE 10

6 lbs. of Sample 4 and 6 lbs. of Sample 5 were tumble blended, extruded,molded and tested as in Example 1. The results are presented in TableII.

EXAMPLE 11

4 lbs. of Sample 4 and 8 lbs. of Sample 1 were tumble blended, extruded,molded and tested as in Example 1. The results are presented in TableII.

EXAMPLE 12

12 lbs. of Sample 5 was extruded, molded and tested as in Example 1. Theresults are presented in Table II.

                                      TABLE II                                    __________________________________________________________________________                HARDNESS NOT. IZOD TENSILE BRITTLE                                                                              VICAT                           FLEX. MOD.  SHORE D  (ft-lbs/in)                                                                             (psi)   TEMP   SOFT. PT.                                                                           SHRINK                                                                              RESIL               EX. (psi × 10 - 3)                                                                  (10/SEC. DEL.)                                                                         ROOM -29° C.                                                                     Yield                                                                             Break                                                                             (°F.)                                                                         (°C.)                                                                        (%)   (°)          __________________________________________________________________________    Cl  53.0    46.5     DNB  PB   2397                                                                              1925                                                                              <-96    93   0.62  13.0                1   36.1    45.0     DNB  PB   2095                                                                              2121                                                                              <-96    94   0.75  11.0                2   65.7    54.7     3.5  0.88 3120                                                                              2384                                                                              -22    118   1.17  14.2                3   49.5    50.8     DNB  1.10 2486                                                                              2294                                                                              -54    104   1.20  13.6                4   53.0    49.8     PB   1.60 2490                                                                              2203                                                                              -51    102   1.12  13.8                5   62.8    52.0     PB   1.90 2749                                                                              2053                                                                              -78    115   1.11  13.0                C2  75.5    58.5     2.4  0.48 3605                                                                              2401                                                                              12     116   1.28  14.0                6   28.3    41.0     DNB  PB   1639                                                                              1927                                                                              <-96    80   1.07  10.5                7   48.7    51.5     DNB  0.99 2588                                                                              2338                                                                              -35    108   1.25  13.0                8   33.8    42.5     DNB  PB   1923                                                                              2014                                                                              <-96    80   0.88  11.0                C3  49.2    53.5     PB   0.49 2787                                                                              2298                                                                              -20    107   1.32  12.1                9   38.3    47.0     DNB  2.30 2131                                                                              2203                                                                              -78     95   1.20  11.5                10  30.3    43.2     DNB  1.88 1966                                                                              2151                                                                              -69     96   1.21  11.6                11  50.2    48.5     DNB  2.10 2491                                                                              2275                                                                              -68    103   1.09  13.5                12  17.8    36.7     DNB  PB   1274                                                                              1644                                                                              <-96    70   1.12   9.5                __________________________________________________________________________     DNB = did not break                                                           PB = partial break                                                       

These examples generally show that the thermoplastic olefin alloys inaccordance with the present invention provide a similar or improvedcombination of resiliency, impact strength, flexibility, heat distortionresistance, surface hardness and elasticity properties as do thestandard thermoplastic olefin compositions as typified by ComparativeExample 1. Further, the TPO alloys of the present invention accomplishsuch combination of properties by utilizing less OCE than theconventional composition, generally meaning that the present TPO alloyswill have improved cosmetic and moldability characteristics at lesscost.

Many modifications and variations besides the embodiments specificallymentioned may be made in the compositions and methods described hereinand depicted in the accompanying drawing without substantially departingfrom the concept of the present invention. Accordingly, it should beclearly understood that the form of the invention described andillustrated herein is exemplary only, and is not intended as alimitation on the scope thereof.

What is claimed is:
 1. A process for producing a thermoplastic olefinalloy, comprising the steps of:feeding propylene, ethylene and acatalyst to a first reactor to at least partially copolymerize saidpropylene and ethylene to produce a first random propylene/ethylenecopolymer, thereby generating an outlet stream comprising said firstrandom copolymer, unreacted propylene, unreacted ethylene and saidcatalyst; feeding said outlet stream, additional propylene andadditional ethylene into a second reactor to produce a reactor blend ofsaid first random copolymer with a second random propylene/ethylenecopolymer, said reactor blend having an ethylene content of from 3% to8% by weight and an MFR of less than 1; blending from 50% to 88% byweight, based upon the weight of said alloy, of said reactor blend, from12% to 23% by weight, based upon the weight of said alloy, of an olefincopolymer elastomer, and from 0% to 33% by weight based upon the weightof the alloy, of polypropylene; and increasing the MFR of said alloy byblending said alloy in the presence of an organic peroxide.
 2. Theprocess according to claim 1, wherein said reactor blend has an MFR ofless than 0.1.
 3. The process according to claim 1 or 2, wherein the MFRof said reactor blend is increased by blending said reactor blend withsaid organic peroxide before said reactor blend is blended with saidolefin copolymer elastomer, the MFR of said reactor blend beingincreased to from 1 to
 35. 4. The process according to claim 1 or 2,wherein said MFR of said alloy is increased from 1 to
 35. 5. A processfor producing a thermoplastic olefin alloy, comprising the stepsof:feeding propylene, ethylene and a catalyst to a first reactor to atleast partially copolymerize said propylene and ethylene to produce afirst random propylene/ethylene copolymer, thereby generating a firstoutlet stream comprising said first random propylene/ethylene copolymer,unreacted propylene, unreacted ethylene and said catalyst; feeding saidfirst outlet stream, additional propylene and additional ethylene into asecond reactor to produce a first reactor blend of said first randompropylene/ethylene copolymer with a second random propylene/ethylenecopolymer, thereby generating a second outlet stream comprising saidfirst reactor blend, unreacted propylene, unreacted ethylene and saidcatalyst, said first reactor blend having an ethylene content of from 3%to 8% by weight and an MFR of less than 1; feeding said second outletstream, a monoolefin selected from one or more of C₃ to C₁₀alpha-olefins, and ethylene into a third reactor to produce a secondreactor blend of said first reactor blend with an olefin copolymerelastomer; and increasing the MFR of the reactor blend to from 1 to 35by blending the reactor blend in the presence of an organic peroxide. 6.The process according to claim 5, wherein said alloy comprises from 70%to 88% by weight, based upon the weight of said alloy, of said firstreactor blend.
 7. The process according to claim 5 or claim 6, furthercomprising blending said second reactor blend with from 0% to 33% byweight, based upon the weight of said alloy, of polypropylene.
 8. Theprocess according to any of claims 5 to 7, wherein said first reactorblend has an MFR of less than 0.1.
 9. The process according to any ofclaims 5 to 8, further comprising feeding a non-conjugated diene intosaid third reactor.
 10. The process according to any of claims 5 to 9,further comprising the step of removing said unreacted propylene fromsaid second outlet stream prior to feeding said second outlet streaminto said third reactor.